It has been found that the best way to impart an electrostatic charge to paint is to produce air ions that are intimately mixed with the paint particles that can be either liquid or solid. To this end, needle electrodes connected to a high voltage source have been used in prior art electrostatic spray guns. The best result seems to have been achieved when a sole properly located needle electrode has been used. Alternatively, the paint nozzle itself has been utilized as an electrode in some prior art spray guns. Then, the nozzle has been made of metal and connected to high voltage. This is a more robust construction but it is not as efficient as the ones having needle electrodes. In one prior art spray gun for liquid paint, a sole needle electrode extends axially through the discharge orifice of the nozzle. Although its charging properties are good, the electrode has disadvantages. One major disadvantage is that the paint pattern is seriously biased when the needle is not quite coaxial with the discharge orifice.
It is an object of the invention to provide electrostatic spray guns which efficiently charge the liquid or solid paint particles and which withstand negligent handling without their charging efficiency becoming decreased. Another object is to provide a simple and reliable connection of high voltage to the charging electrodes of an electrostatic spray gun. An ancillary object is to provide an electrostatic spray gun which in use is not apt to produce sparking.